Facebook Games and Your Email Address

I was doing my regular check with my favorite Facebook games and I noted some new messages while the games loads

Give your email address to FishVille?
Soon, applications won’t be able to send you notifications on Facebook. If you like, you can start receiving emails directly from FishVille.
Emails will be sent to: my Facebook contact email ([email protected])

The message appears when you try Petville and Café World. The email address given is the one I used in registering with Facebook. I consider this information quite confidential and my security-first mindset hinted that I should be paranoid-mode today so I clicked the NO Button.

It is interesting to note that in FishVille they even “encourage” you further by giving away a special fish (Dwarf Angelfish) if you will send your email address to them

So what’s cooking in the café of Facebook and the Game Developers?
Is this “games/apps asking for email address message” isolated to Zynga Games only?
Feel free to share your comments here.